This invention relates generally to a television receiver and more particularly to a vertical synchronizing control circuit for generating stable, precise vertical synchronizing control signals for the display device. In the prior art, an internally generated vertical sync signal is synchronized in phase with the external vertical sync signal by directly resetting a divider circuit. The divider circuit divides a frequency which is a multiple of the horizontal sync signal fH. Therefore, if the external vertical sync signal includes noise, the divider circuit is reset not only by the external vertical sync signal, but also by noise carried with that signal. This results in the occurrence of a false internal vertical sync signal which is synchronized to the noise and stable vertical synchronization is not achieved for the display device. Also, if the externally received signal fades, there may not be always vertical sync signal generated internally.
What is needed is a vertical synchronizing control circuit which provides stable sync signals for a display device regardless of noise or weakness in the externally received television transmission and its vertical sync signal.